Spotify stops playing

[ZB17]

When I'm listening to my music on my phone, Spotify randomly stops playing music, but you can see that the song is still running. It just doesn't give a sound. After 20 seconds the music starts again. Everything is up to date, so I don't understand why the app does this.
It happens the most when I pick up my phone or lay it down again, but also other times. Does anyone have any ideas?